The present invention relates to a restraint system for a motor vehicle having sensors for detecting a collision of the motor vehicle, and a control unit for analyzing signals of the sensors.
A restraint system for vehicles is described in U.S. Pat. No. 5,326,146. In this restraint system, the data of sensors provided in the vehicle is analyzed by a control unit to determine a possible collision of the vehicle. If a collision is recognized, the control unit activates a first restraint device and, after a predefined time interval, a second restraint device. In addition, the activation or triggering of the first restraint device is monitored using a malfunction monitoring unit. If a malfunction is recognized upon the triggering of the first restraint device, the control unit immediately activates the second restraint device, i.e., without a time delay. In this restraint system, only a malfunction of the first restraint device is taken into consideration.
The present invention provides an improved restraint system which also considers a malfunction upon the triggering of the second restraint device.
The restraint system for a motor vehicle according to the present invention includes sensors for detecting a collision of the motor vehicle, and includes a control unit, which analyzes the sensor signals and transmits a first signal to a safety belt retention device as a first retention device in the event of a recognized collision of the motor vehicle, and activates a belt tensioner using a predefined first retention force. It then transmits a second signal to a front airbag system as a second retention device, which then triggers a front airbag after a predefined time interval following the activation of the belt tensioner. The system includes a malfunction monitoring unit for one of the retention devices, such that the control unit transmits a third signal to a replacement retention device, which then activates a replacement actuator, in the event a malfunction of the front airbag system is recognized by the malfunction monitoring unit.
An advantage of the restraint system according to the invention is that in the event of a malfunction of the front airbag system, the vehicle occupant(s) is (are) nonetheless well protected in the event of an accident. As is the case in already known restraint systems, signals of various sensors provided in the vehicle are analyzed with regard to an accident or a collision. The sensors may be acceleration sensors or pressure sensors, for example, which are installed in the vertical direction of the vehicle. The restraint system is implemented in such a way that upon recognition of a collision of the vehicle, the control unit first transmits a first signal to a safety belt restraint device, and subsequently transmits a second signal to the front airbag system. The safety belt restraint device activates an actuator for tensioning the belt, i.e., a belt tensioner, using a predefined first restraint force, upon transmission of the first signal. This is to prevent the driver from hitting the front airbag triggered by the second signal of the control unit unbraked, i.e., with too much energy. The restraint force is not to be too great, however, so that the vehicle occupant is not subject to unnecessary injuries from the restraint, such as broken ribs. Subsequently, the front airbag is triggered, according to the present invention, after a time delay relative to the belt tensioner. The chronological sequence for activating the actuators of the restraint devices is of special significance, in order to provide the occupants with optimal protection. The time delay is typically only very slight. According to the invention, it is unimportant whether the control device outputs the second signal with a delay with respect to the front airbag system activation, or the time delay is performed by the front airbag system itself.
The restraint system may also be implemented in such a way that the control unit triggers either only the first restraint device or, for example in the event of a stronger collision, both the first and second restraint devices as a function of the strength of the collision of the motor vehicle. In the restraint device according to the present invention, it is assumed that both the first and also the second restraint device can be activated or triggered.
If the front airbag does not trigger in response to a second signal transmitted by the control unit, and thus a malfunction of the front airbag system is recognized by the malfunction monitoring unit, the control unit transmits a third signal to a replacement restraint device, which then activates a replacement actuator. The occupant protection is thus further improved.
The replacement restraint device is advantageously the safety belt restraint device, to which the control unit transmits the third signal. Due to the third signal, the safety belt restraint device does not activate the belt tensioner using the predefined first restraint force, but rather using a predefined second restraint force, which is different from the first restraint force.
The second restraint force is advantageously greater than the first restraint force. This prevents the occupants from hitting the steering wheel or the dashboard in the event of a collision and a malfunction of the front airbag system, which could result in severe injuries to the occupants. The safety belt restraint device thus assumes the entire restraint or protective function.
The malfunction monitoring unit is advantageously implemented as an airbag triggering circuit monitoring unit, or as an interior sound pressure propagation monitoring unit using a microphone. Implementing the malfunction monitoring unit as an airbag triggering circuit monitoring unit offers the advantage that a malfunction may thus be recognized with a very high probability. If the malfunction monitoring unit is implemented as a sound pressure propagation monitoring unit, a microphone already provided in the vehicle, such as the microphone of the telephone system, may be used without incurring any additional costs.
The method for operating the restraint system according to the present invention will be discussed in the following description and figures, and will be explained in greater detail with reference to the drawings.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.